A method and apparatus for modifying low emissivity (low-E) coated glass, so that windows using the processed glass allow uninterrupted use of RF devices within commercial or residential buildings. glass processed in the manner described herein will not significantly diminish the energy conserving properties of the low-E coated glass. This method and apparatus disrupts the conductivity of the coating in small regions. In an embodiment, the method and apparatus ablates the low-E coating along narrow contiguous paths, such that electrical conductivity can no longer occur across the paths. The paths may take the form of intersecting curves and/or lines, so that the remaining coating consists of electrically isolated areas. The method and apparatus are applicable both to treating glass panels at the factory as well as treating windows in-situ after installation.
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1. A method of removing or creating an absence of a portion of a low emissivity (low-E) coating from a sheet of glass, comprising:
removing or creating an absence of a portion of the low-E coating in a pattern of intersecting lines or curves, in a manner that keeps the majority of the glass coated by the low-E coating, where all the lines or curves are interconnected and leave behind a plurality of areas of the coating that are permanently electrically isolated by the removal or absence of the portion of the coating and that remain electrically isolated while the glass is in use, wherein the removed portion or absence of the coating is of a size and shape such that the coated sheet of glass allows transmission, through the glass, of cellular and wireless local area network (Wi-Fi) radio signals with an insertion loss of 10 db or less.
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In the interests of conserving energy, windows with a low emissivity (low-E) coating have grown in popularity over the years. Such windows are now common in new commercial construction. These windows offer the benefits of conserving energy and money by reducing the need for air conditioning and/or heating. However, such windows have a severe impact on radio frequency (RF) signals. The coatings that are applied to window glass to transform it to a low-E window are comprised mainly of metals. Although the coatings are thin and transparent, their metallic content is effective at conducting electricity. This makes the coatings efficient reflectors of broad bands of radio frequency signals. Signals transmitted through the windows can be attenuated at levels of 30 decibels (dB) or more. Furthermore, commercial construction tends to use other materials that further block RF signals. Materials such as concrete, brick, mortar, steel, aluminum, roofing tar, gypsum wall board, and some types of wood all offer varying degrees of RF absorption. The result is that many newer commercial buildings severely impede RF signals from getting into or out of the buildings.
Nonetheless, RF devices have become an important part of modern life, especially with the emergence of smartphones, which have a variety of RF devices built-in. Such devices may include cellular transceivers, wireless local area network (“wi-fi”) transceivers, Global Positioning System (GPS) receivers, Bluetooth transceivers and, in some cases, other RF receivers (e.g., FM/AM radio, UHF, etc.). As the popularity of such devices has grown, the importance of being able to use RF-based features within the confines of modern commercial buildings has grown.
Currently there are several commercially available techniques to facilitate the use of smartphones or similar devices within affected buildings. All of these techniques pose challenges, both for the installer as well as the user, depending on the technique. They include the following:
First, an external antenna can be connected to most cell phones in order to improve antenna gain. However, there still must be sufficient signal within the building and the cell phone must remain connected via a cable. This solution can be inconvenient and has performance limitations in some circumstances.
Second, a femtocell can be used. A femtocell is a device that resembles a wireless router and can be purchased from mobile service providers. This device connects to an existing broadband internet connection in a home or office, and radiates cell phone signals to a maximum range of about 40 feet. The maximum coverage per device is approximately 5000 square feet. Depending on the mobile provider, these devices can support between four and 16 simultaneous calls and require data bandwidths of greater than 1.5 Mb/s. Typically, prepaid phones are not supported with this solution. Also, these devices must be located near a window to provide a GPS signal. However, while a femtocell will support cellular signals, low-E coated windows still block GPS signals. This latter problem can be addressed by an external GPS antenna connected to the femtocell. Although connections initiated via the femtocell automatically connect to cell towers when the phone moves outdoors during a call, it does not work the other way—calls are dropped if the connection is established outdoors via a cell tower and the phone is then moved indoors where a femtocell is located. Another disadvantage of using femtocells in office buildings is that they are not universal for all mobile providers. A different femtocell must be purchased and set up for each provider.
The third solution is the deployment of a cellular repeater or booster that consists of an external antenna, a bi-directional amplifier, and internal antennas for re-transmission. These can be installed by individual carriers, whose equipment will only work for that carrier, or by independent installers who can provide multi-carrier and multi-band equipment. Second generation (2G) and third generation (3G) technologies all operate in the 850 MHz (cellular) and 1900 MHz (PCS) bands. All major carriers (e.g., Verizon, AT&T, Sprint and T-Mobile) operate in this dual-band region. Fourth generation (4G) systems operate at 700 MHz, 1700/2100 MHz and require different antennas than the 2G/3G dual bands. Most currently deployed repeaters were designed for 3G technology and do not operate at 4G frequencies. 5-band amplifiers, which operate over both 3G and 4G bands, have recently become available, but are likely not compatible with currently deployed antennas and will probably be incompatible with the next generation of cellular hardware. Cellular repeaters also do not boost Wi-Fi, WiMax and other signals in the 5 GHz band. In general, the use of repeaters will constantly require upgrades as technology advances.
There are additional limitations to the use of repeaters. Most applications require a custom installation. There must be room for antennas to be placed on the roof and cables must be run from them to interior locations. There is also a tradeoff between using antennas which provide a high gain but are unidirectional, and thus only boost signals from a single cell tower, and omni-directional antennas that provide less gain. The strongest amplifiers have enough gain to provide indoor coverage of up to about 100,000 square feet. This number is typically much lower, though, due to interior building materials that provide obstacles to the signal and unusual building geometries. In addition, concrete and steel floors significantly attenuate the signals, resulting in the need for separate amplifiers on every floor. Moreover, the cost of outfitting a commercial building can exceed $10K per floor.
In the drawings, the leftmost digit(s) of a reference number identifies the drawing in which the reference number first appears.
An embodiment is now described with reference to the figures, where like reference numbers indicate identical or functionally similar elements. While specific configurations and arrangements are discussed, it should be understood that this is done for illustrative purposes only. A person skilled in the relevant art will recognize that other configurations and arrangements can be used without departing from the spirit and scope of the description. It will be apparent to a person skilled in the relevant art that this can also be employed in a variety of other systems and applications other than what is described herein.
The following describes a method and apparatus for modifying low-E coated glass, so that windows using the processed glass allow uninterrupted use of RF devices within commercial or residential buildings. The method and apparatus are applicable to treating glass panels at the factory before installation, as well as treating windows in-situ after installation. At the same time, glass processed in the manner described herein will not significantly diminish the energy conserving properties of the low-E coating.
This method and apparatus for improving RF transmission through low-E coated glass involves a permanent change to the low-E coating on the window. The coating is normally conductive over the entire area of the glass; this method and apparatus disrupts the conductivity of the coating in small regions. In an embodiment, the method involves ablating the low-E coating along narrow contiguous paths, such that electrical conductivity can no longer occur across the paths. The paths may take the form of intersecting curves and/or lines, so that the remaining coating consists of electrically isolated areas.
In an embodiment, this process is performed using a pulsed laser to remove (i.e., ablate) the low-E coating. In this method, the pulsed laser is focused onto the surface of the sheet of glass where the coating is located. With each pulse of the laser, a small (e.g. 20-25 micron diameter) circular spot is ablated from the glass, permanently removing it. In alternative embodiments, the ablated spot may be anywhere from 10-200 microns in diameter. By pulsing the laser many times per second (e.g. 100 kHz in an embodiment), while simultaneously moving the laser over the low-E coating, a path of overlapping ablated spots results, creating the appearance of a thin line (in much the same manner that a laser printer creates the appearance of a line on paper). The line can be straight or curved, and normally for a large window there will be many such lines that are ablated, with the spacing of the lines or curves depending on the desired characteristics of the RF reception through the glass.
Due to the nature of low-E coatings, their energy conserving properties are largely unaltered by such ablation if the total area of ablation is kept small. For example, if a window has a series of lines ablated into the coating, but the total area of the lines is kept small (e.g. <2% of the total glass area), then the impact to the energy conserving properties will be similarly small, and therefore acceptable for most applications.
The impact on RF signal transmission through the window, however, is not a simple function of ablated area. For example, a low-E coated window that has had only 1% of its area ablated with a regular grid pattern can experience a much greater throughput benefit than might be suggested by only having 1% of the area ablated. RF testing has confirmed that this is the case, showing that for some ablation patterns, a 1% area ablation of simple grid lines can change the insertion loss of such a window from over 35 dB (less that 1/10th of 1% throughput) prior to ablation to less than 10 dB (nearly 10% throughput) after ablation, which is a significant improvement. Alternatively, a low-E coated window that has had 1% of its area ablated will only have its infrared-reflecting properties reduced by 1%. Therefore a very small change to the infrared properties of the low-E coating can result in a very large benefit in the RF transmission properties.
In an embodiment, a pulsed laser may be used, where each pulse delivers enough energy to ablate a spot of the low-E coating 120. The laser is moved in a plane that is approximately parallel to the glass as it operates. The laser moves across the glass in a linear or curvilinear manner. The result is shown in
The pattern of ablated intersecting paths may be varied. Various grid-like patterns that may be used are illustrated in the embodiments of
In alternative embodiments, the ablated intersecting paths are not necessarily limited to horizontal and vertical line segments. As shown in the embodiment of
In embodiments, the ablated area of a window may be 2% or less of the total area. In other embodiments, a different percentage may be used (e.g. 5% or less total area of a low-E coating removed, and 95% total area of a glass sheet retaining the low-E coating). Note that while ablation of a higher percentage of the area may improve the transmission of RF signals through the window, ablation of more of the low-E coating diminishes the energy conserving properties of the window.
In embodiments, the grid spacing can be range from 2-10 mm. In general, smaller isolated areas of low-E coating facilitate improved RF transmission at shorter wavelengths, whereas larger overall size of the entire ablated pattern tends to facilitate longer wavelengths. Patterns that need to allow for transmission of multiple RF frequencies, while providing maximum transmission across all those frequencies, may have an overall ablation area dictated by the longer wavelengths while simultaneously having the grid/line spacing dictated by the shorter wavelengths.
The overall area of the pattern may vary in different embodiments. Larger patterns, by overall area, generally allow improved RF transmission. In some situations, however, the permissible area for a pattern may be limited. In such a case, transmission of RF signals may still be improved if the pattern area has a length and width in excess of approximately two times the wavelength of the RF signal.
An apparatus for the ablation of low-E coating is illustrated in
Note that in some situations, the coated glass pane 110 may be part of a double pane window. Such a configuration is common in modern construction. The second pane is shown in
The wavelength of the laser used in various embodiments may differ. In some embodiments, the wavelength may be greater than 1400 nm. Such wavelengths have the advantage of providing improved eye safety to the operator and nearby persons compared to shorter wavelengths. In an alternative embodiment, the wavelength may be 1064 nm, which is a commonly used wavelength for marking lasers. Moreover, as noted above, in an embodiment the laser 410 is a pulsed laser. In an embodiment, the pulse width is less than 10 nanoseconds (ns), although pulse widths as great as 100 ns or longer may be used. Further, in an embodiment each pulse delivers at least 3 microjoules (μJ) of energy. In alternative embodiments, values of these parameters may differ as will be understood by a person of ordinary skill in the art.
Ablation may be performed on a window during the manufacturing process or during or after the installation process. In an embodiment, ablation may be performed on a window that is already in place in an existing wall. An apparatus 500 for performing this process in such a context is illustrated in
In the illustrated embodiment, the pulsed laser 410 is attached to a rail 540 in a manner that allows the laser to slide or otherwise move along the length of this rail. In particular, the pulsed laser 410 and lens array 440 may be attached to a mount 570 that is attached to a belt 560 incorporated into this rail length wise. The belt 560 may be mounted on two pulleys, 550a and 550b at either end of rail 540. The belt 560 is therefore movable; movement of the belt serves to move the pulsed laser 410 and lens array 440 mounted thereon. One of the pulleys may be driven by a motor 545. In the illustrated embodiment, motor 545 turns pulley 550a, thereby driving the belt 560. This in turn moves the pulsed laser 410 and its lens array 440 along the length of rail 540 (up and down in the illustrated embodiment). The motor 545 maybe capable of turning in either direction, so that the belt 560 may move in either direction, as shown. In this way, the laser 410 may be moved in either direction along rail 540. In an alternative embodiment, the motor 545 may be mounted at the opposite end of rail 540 to drive pulley 550b. In yet another embodiment, two motors may be used, one at each of pulleys 550a and 550b, and operating in synchronicity.
In the embodiment of
Here, rail 510a includes a belt 520a that is mounted on two pulleys 515a and 515b at either end of rail 510a. The mount 530a is attached to this belt. Similarly, rail 510b includes a belt 520b that is mounted on two pulleys 515c and 515d at either end of rail 510b. The mount 530b is attached to this belt. Pulley 515c is driven by a motor 512b. This serves to move belt 520b. Likewise, pulley 515a is driven by a motor 512a, which serves to move belt 520a. By synchronizing the actions of motors 512a and 512b, belts 520a and 520b may be simultaneously moved in the same direction at the same speed. Given that rail 540 is mounted on the belts 520a and 520b, this serves to move rail 540. The motors 512a and 512b can turn in either direction; this allows respective belts 520a and 520b to move in either direction, as shown. As a result, rail 540 (and pulsed laser 410 and lens array 440, which are attached to this rail) can be moved from side to side in the illustrated embodiment.
In alternative embodiments, motors 512a and 512b may instead be attached to pulleys 515b and 515d. Moreover, in other embodiments, any or all of the pulleys 515a-515d may be driven by motors that are synchronized to one another.
The combined motions of belts 520a, 520b, and 560 allow the pulsed laser 410 and lens array 440 to move about in a two-dimensional plane that is essentially parallel to the window. By controlling the speed and direction of motors 512a, 512b, and 545, the laser 410 and lens array 440 can be made to move over the window in any desired path. By energizing the pulsed laser 410 while in motion, a path can be ablated in the low-E coating of this window.
In in an embodiment, the motors 512a, 512b, and 545 may be controlled by a programmable computer (not shown). By programming this computer appropriately, the computer can be made to create and deliver control signals to these motors to control the motion of the pulsed laser 410 and lens array 440, and thereby control the path and pattern of ablation. For example, the apparatus 500 may be used to create any of the patterns illustrated in
As noted above, other patterns may be created, different from or in addition to these. In an embodiment, the pulsed laser 410 and lens array 440 can be made to move at an overall speed of 1 m/s; other speeds are possible.
In an embodiment, the motors illustrated in
Also, while
One end of rail 540 is mounted on belt 520a, which is in turn mounted on a pulley 515a and a pulley 515b (not shown). These pulleys, along with belt 520a, are incorporated in rail 510a. The near end of this rail is attached to the window by a mount 507a and support block 610. A similar mounting configuration may be in place at the far end of rail 510a. Pulley 515a is turned by motor 545a, thereby moving belt 520a and rail 540. A similar configuration is present at the opposite end of rail 540. As stated above, this allows for horizontal movement of pulsed laser 410 and lens array 440.
In embodiments, the laser 410 may be supported by a spring mechanism (not shown). For example, a constant force spring may be used along the y-axis to support the laser 410 and reduce mechanical stress in the illustrated system.
Note that all the rails are approximately parallel to the glass. This allows the laser to operate in a plane that is approximately parallel to the glass, maintaining the focused laser spot on the low-E coating across the entire ablation pattern area. In embodiments, the rails are within 500 microradians of parallel.
While the embodiments described above address ablation using a mechanically scanned laser, in alternative embodiments other methods may be used to remove or create the absence of a low-E coating to achieve the results exemplified in
Another embodiment for achieving the results exemplified in
An alternative process for achieving some transmission of RF signals through a low-E coated window is to purposely fabricate the glass with large areas free of low-E coating. An example that would provide some benefit is to leave a border around the entire edge of the window that is not coated.
As noted above, the processing of a sheet of glass according to some of these methods may be performed on an installed window. Any of the techniques may be performed at a factory prior to installation. In this latter case, the processing may be completed on a single glass sheet at a time, or an assembly line style operation may be used. Here, multiple stations may be involved. Each station would perform ablation (or removal by other means) of the low-E coating along one or more paths, then would send the glass sheet to another station, where removal of the coating along one or more other paths may be performed, and so on. As would be understood by a person of ordinary skill in the art, such an arrangement would improve throughput at a processing or manufacturing facility.
Methods and systems are disclosed herein with the aid of functional building blocks illustrating the functions, features, and relationships thereof. At least some of the boundaries of these functional building blocks have been arbitrarily defined herein for the convenience of the description. Alternate boundaries may be defined so long as the specified functions and relationships thereof are appropriately performed.
While various embodiments are disclosed herein, it should be understood that they have been presented by way of example only, and not limitation. It will be apparent to persons skilled in the relevant art that various changes in form and detail may be made therein without departing from the spirit and scope of the methods and systems disclosed herein. Thus, the breadth and scope of the claims should not be limited by any of the exemplary embodiments disclosed herein.
Winsor, Robert, Estinto, Eugenio
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Oct 02 2013 | ESTINTO, EUGENIO | ERITEK, INC | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 031332 | /0092 | |
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